1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an LCD device for preventing light leakage due to the flexure of a liquid crystal panel.
2. Discussion of the Related Art
With the advancement of various portable electronic devices such as mobile terminals and notebook computers, the demand for Flat Panel Display (FPD) devices applied to the portable electronic devices are explosively increasing.
LCD devices, plasma display panels (PDPs), field emission display (FED) devices, and light emitting diode (LED) display devices are actively researched as FPD devices. In such FPD devices, the application fields of LCD devices are being expanded because the LCD devices are easily manufactured, have good drivability of drivers, and realize an high-quality image and a large screen.
LCD devices include a first substrate, a second substrate, and a liquid crystal layer formed between the first and second substrates. The LCD devices are devices in which the alignment of liquid crystal is adjusted with an electric field applied to the liquid crystal layer, and thus, light transmittance is adjusted, thereby displaying an image.
LCD devices are variously developed in a twisted nematic (TN) mode, a vertical alignment (VA) mode, an in-plane switching (IPS) mode, or a fringe field switching (FFS) mode according to a scheme of adjusting the alignment of liquid crystal.
In IPS-mode or VA-mode LCD devices among the above-described LCD devices, a lower polarizer and an upper polarizer are respectively attached to both surfaces of a liquid crystal panel such that the 0-degree optical axis of the lower polarizer crosses the 90-degree optical axis of the upper polarizer. In the IPS-mode or VA-mode LCD devices, the flexure of the liquid crystal panel is caused by a contraction difference between the lower polarizer and the upper polarizer in a thermal environment or a wet-heat environment. In the IPS-mode or VA-mode LCD devices, since the lower polarizer and the upper polarizer are respectively attached to both surfaces of the liquid crystal panel such that the 0-degree optical axis of the lower polarizer cross the 90-degree optical axis of the upper polarizer, the vertical axis direction of the upper polarizer is asymmetric with that of the lower polarizer. For this reason, in the IPS-mode or VA-mode LCD devices, the overall flexure of the liquid crystal panel occurs in a direction in which flexure is large.
In the IPS-mode or VA-mode LCD devices, the flexure of the liquid crystal panel becomes the major cause of light leakage. To provide a detailed description, in the IPS-mode or VA-mode LCD devices, as described above, since the liquid crystal panel is bent, a stress is applied to the liquid crystal panel in fixing the liquid crystal panel to a backlight unit. In this case, with a voltage not being applied to the liquid crystal panel, liquid crystal injected into the liquid crystal panel has fluidity, and thus, the liquid crystal becomes non-uniform due to the stress. Particularly, the IPS-mode or VA-mode LCD devices displays a black screen when a voltage for driving liquid crystal is not applied, and thus, light leakage due to non-uniformity of the liquid crystal is discerned with naked eyes.
Hereinafter, a related art LCD device will be described in detail with reference to FIGS. 1 and 2.
FIG. 1 is a perspective view schematically illustrating a related art LCD device. FIGS. 2A and 2B are sectional views taken along line A-A′ of FIG. 1.
Referring to FIG. 1 and FIGS. 2A and 2B, a related art IPS-mode or VA-mode LCD device 100 includes a backlight unit 110, an adhesive layer 120, and a liquid crystal panel 130.
The backlight unit 110 includes a light source for supplying light to the liquid crystal panel 130, and an optical sheet for uniformly supplying light, emitted from the light source, toward the liquid crystal panel 130.
The adhesive layer 120 is formed between the backlight unit 110 and the liquid crystal panel 130 in a double-sided adhesive tape type. In this case, a bottom of the adhesive layer 120 is adhered to the backlight unit 110, and a top of the adhesive layer 120 is adhered to a lower polarizer (not shown) adhered to a rear surface of the liquid crystal panel 130.
The liquid crystal panel 130 includes a first substrate with a color filter array formed therein, a second substrate with a thin film transistor (TFT) array formed therein, and a liquid crystal layer formed between the first and second substrates.
The liquid crystal panel 130 is disposed on the backlight unit 110 with the adhesive layer 120 formed therein, and coupled to the backlight unit 110 with the adhesive layer 120. In this case, as illustrated in FIG. 2B, the liquid crystal panel 130 is deformed. In the liquid crystal panel 130, liquid crystal becomes non-uniform due to a stress, causing light leakage.